The focus of this proposal will be to exploit the vapor detection technology developed recently at Caltech that forms the basis for a low power, simple, manufacturable, "electronic nose". In this technology, an array of sensors responds to essentially all vapors, but produces a distinguishable response pattern for each separate type of analyte or mixture, much like the mammalian olfactory sense produces such diagnostic patterns and then transmits them to the brain for processing and analysis. Pattern recognition algorithms and/or neural network hardware are used on the output signals arising from the electronic nose to classify, identify, and where necessary quantify the vapor or odors of concern and to associate them with certain disease states associated with volatile biomarkers in the breath or other headspace samples. Due to the present high sensitivity of our electronic nose to biogenic amines (detection levels of 1-10 ppt in a few seconds in room air), which far exceeds that of humans for this class of compounds, we plan to initially explore the use of the sensor arrays to screen for bacterial vaginosis, which has been positively associated with the presence of "fishy" odors that arise from volatile biogenic amines in the headspace above vaginal swabs. In addition, we will advance the science and technology of the electronic nose sensors to obtain still improved sensitivity and time response for other biomarkers, so as to open up further medical application areas and to respond to potential confounding interferences identified by the initial small-scale clinical studies on the targeted, initial demonstration application of the technology.